Two recently defined cell-to-cell contacts, (1) the tubulobulbar complexes and the (2) Sertoli-spermatid junction, will be investigated to obtain a more meaningful understanding of the functional interrelationship between Sertoli cells and between Sertoli cells and developing germ cells. Observed at two levels within the rat testis, tubulobulbar complexes likely undergo formative and regressive changes. The latter may be a necessary step in coordinating the synchronous development of germ cells. It is in part the objective of this proposal to test this hypothesis in the rat. The Sertoli-spermatid junction, only briefly characterized at this point, also undergoes formative and regressive changes during the spermatogenic cycle. This indicates a functional relationship to the developing germ cells. It is also objective of this study to provide additional characterization of this junction in the rat, and to correlate its formation and dissociation with events of the sperm release process. Lastly, it is the objective of this proposal to characterize these cell-to-cell relationships in the guinea pig and monkey. BIBLIOGRAPHIC REFERENCES: Russell, L.D. 1977. Desmosome-like junctions between Sertoli cells and germ cells in the rat testis. Amer. J. Anat, in press. Russell, L.D. 1977. Movement of spermatocytes from the basal to the adluminal compartment of the rat testis. Amer. J. Anat., in press.